My opinion on Parelli? Marketable and exploited. No one can or should sell a method of training for any animal. Its simply not possible! There are so many in-s and out-s to training that any person cannot gain from reading a book or watching a DVD. Even the best videos cannot teach a person about all training all the time.
The actual Parelli "games" are sound though. Not the constant daily use, however. The friendly game: Teaches horse to be okay with you touching them and desensitized to "scary" things touching them. Porcupine game: Moving off pressure. Driving game: More advanced porcupine game because you don't touch the horse. You use this in lunging a lot. YoYo game: I don't specifically agree with the WAY they ask you to do this one, but the idea that a horse should move away from you and come close to you when you ask is good. Circling game: Using pressure from a distance to get a horse to circle around you. Lunging. Sideways game: Sidestepping. Squeeze game: I don't know, but it might just be my lack of experience that tells me this is useless.
The games are mostly credible, but not necessarily the methods they use to obtain them. Parelli has some very sound ideas, but unlike they try to convince you it is not a be-all-end-all method that everyone should use.
"The wise man thinks he knows nothing.
The fool thinks he knows everything."